1. Field of the Invention
The present invention relates to an imaging device such as a camera that is capable of correcting the effects of blurring in picked-up images which are due to vibrations applied to the device.
2. Description of the Related Art
A typical blur-correcting image pickup device is disclosed in Japanese laid open patent application no. 62-47012. The device depicted in the '012 application detects the vibration of the image pickup device, calculates a vibration quantity from the detection result, and performs correction control corresponding to the vibration quantity. The '012 application states that in order to calculate the vibration quantity, it is necessary to know the displacement of the optical axis, and to do so, such factors as blurring due to rotations around a principal point, blurring due to parallel transfer of the principal point, focal distance of the lens, lateral magnifying power, rotary angle of the optical axis, and parallel transfer distance of the principal point are required as well.
The aforementioned '012 application also mentions a focus position detection device and an auto-focus (AF) focusing device which incorporate through the lens (TTL) focus detection device methods. In such TTL focus detection methods, the focus position detection device generates an output of the lateral magnifying power (.beta.) to the control circuit. It detects the positioning motion of the focusing optical system controlled by the focusing drive of the AF focusing device, and uses it to calculate the blurring quantity to be corrected. In other words, in order to calculate the blurring quantity, such prior art devices require a detection device to monitor the lens focus position continuously, to output a data signal of the lateral magnifying power, and to conduct the blur quantity calculation continuously based on the output.
As such, the prior art devices mentioned above incorporate the following problems. First, it is troublesome to continuously monitor the motion of the focusing optical system as it demands a large information processing capability for a control circuit, It is not easy to provide a high performance CPU in a camera, especially in regard to the costs associated with including a high performance CPU in a mass-produced camera product.
Second, the lens-shutter camera (hereinafter "LS camera"), which is becoming increasingly popular, measures object distance by the triangulation method using external light by resorting to a complicated procedure, that involves distance measuring operations, calculation operations, focusing drive operations and detection of the focusing motion.
Third, the positioning motion of the LS camera is often designed as a stepping motion, so that it is not quite necessary to detect the motion continuously, but rather it is sufficient to store simply the stepping position in the memory.
In case of the LS camera equipped with a so-called "infinite distance shooting mode" feature (a popular feature of the typical LS camera), which is useful in case the AF focusing device may not work (e.g., in picture taking situations across a window), selecting the infinite distance shooting mode automatically specifies the position of the focusing system so that storing the specified step position in memory suffices the above-mentioned purpose.
Also, in case of a camera equipped with "close-up" and "portrait" modes, it is sufficient to keep those specific step positions in the memory and to not continuously monitor optical axis shifts caused by camera vibration.